Over the past two years, Allentown has seen almost runaway development that has $1 billion being spent to dot the downtown with a collection of new buildings that would have been unthinkable just a few years ago.

The building has been so fast and so furious that its downtown arena authority is shifting its focus from figuring out how to develop its long-struggling business district to envisioning what it should look like when it's done.

A master plan being drafted has members of the Allentown Neighborhood Improvement Zone Development Authority considering how to mold the new downtown into a place where people will not only want to work, but also to walk their dog.

That will likely mean a softening of its concrete, corporate look by installing build height limits and new design rules to make it a more inviting place for pedestrians and less imposing to the neighborhoods around it.

"For 20 years Allentown was so desperate for anything that raised tax base, it pretty much had to accept anything presented," said ANIZDA board member Alan Jennings. "Well, we're not desperate anymore. We're in a position to step back, and maybe dictate a little bit to developers the vision we have for the future."

Urban design consultants Goody Clancy of Boston have been devising a new master plan of how the city's growing business district should evolve. ANIZDA Executive Director Sara Hailstone said the plan, expected to be complete by the end of the year, may help city zoning and planning officials review future projects. But it will be especially helpful to ANIZDA members who offer massive tax incentives to developers willing to rebuild the downtown the way they envision it.

It will allow the ANIZDA board to encourage some concepts the downtown hasn't seen before, and some that have worked in the past, said Ben Carlson, director of urban design at Goody Clancy.

There will likely be restrictions on how high developers can go in some neighborhoods, a call for more street trees and pocket parks and recommendations to use unusual designs such as buildings that taper away from the sidewalk.

"If you want people to live and work downtown, you have to make it walkable and inviting," Carlson said. "People don't want to walk past blank walls and empty parking lots while traffic whizzes past."

The next public hearing on the master plan is scheduled for Nov. 24, but some design concepts that ANIZDA can use will almost certainly make the cut.

Perhaps the most foreign to Allentown will be tall buildings that "step back" from the street. To avoid causing a closed-in, concrete feel, taller buildings of more than six stories can taper back 10 to 15 feet from the sidewalk after the third or fourth floor, allowing in more light and presenting a brighter view of the streetscape, Carlson said.

Another recommendation will restrict building heights to provide a smoother transition into the surrounding neighborhoods.

"In general, in the heart of the downtown, near Hamilton and Seventh, the sky's the limit," Carlson said. "But as you get closer to the homes, as you approach Turner and Walnut, you restrict the heights. You don't want to cast giant shadows into the neighborhoods or have a situation where people have to sit on their porch and stare at a 10-story wall."

That would seem to conflict with the current plan by developer Bruce Loch to build the Lehigh Valley's tallest building, a 33-story office complex on a small, 4,000 square-foot lot at Ninth and Walnut streets. Not only would it sit directly across the street from homes, but because it is on such a small lot, Loch plans to widen the building on the upper floors by having them cantilever over the sidewalk after the seventh floor. If ANIZDA members who already less-than-affectionately refer to it as "the needle" want a professional opinion to back their dislike for it, they'll probably to get it in the master plan.

That doesn't seem to faze Loch.

"I'd have to see their master plan, but I know we have a viable project," Loch said Friday.

The plan will also recommend more street trees and grassy patches and street parking wherever possible, to provide a buffer between traffic and the sidewalk.

And ANIZDA members are anxious to apply new technology that would enable them to require developers to not only provide a rendering of how their building will look, but also a block-long rendering of the buildings around it.

"When we see a rendering presented to us, the building often looks great," said ANIZDA chairman Sy Traub. "But how does it look in the streetscape? Maybe it's not compatible, and we're not seeing it because we don't have the full picture. This would change that."

It's unclear whether any of these new concepts will simply serve as a planning tool, or whether some will be incorporated into planning and zoning laws to become requirements.

The reason it's so important to ANIZDA is that it has unique discretion to unilaterally incorporate its recommendations in its approval process. In the 127-acre NIZ, developers are free to tap most new state taxes generated from their projects to pay their building costs. It's a massive, one-of-a-kind tax incentive that is helping to fund the $177 million arena, several office buildings, restaurants, shops and a hotel.

Part of its power, and the importance of the new design regulations, is the authority's ability to deny those benefits.

"It's good to be in a position to say 'no'," Carlson said, "because that gives you the power to say 'yes, if you do it our way.' "